Cellular communication networks typically comprise a network of base stations, each covering a certain geographic area (cell). Communication occurs usually between base stations and user equipment under the general control of a network controller and network managed from element management system (EMS) or network managements system (NMS). In this way, planners can locate base stations so as to operate in a way that provides coverage for particular populations within the context of a wider geographical area.
The invention has particular, but not exclusive application to self-organising networks (SON) using 3GPP (3rd Generation Partnership Project) and NGMN (Next Generation Mobile Networks). Coverage hole detection recovery is a use case in 3GPP and NGMN. Use case is about automatic detection of coverage holes in the network and automatic fixing of the hole.
The optimum coverage areas of cells may change for various reasons. On-going urbanisation, for example, may lead to holes developing in a cellular network. Other factors which lead to necessary changes that have to be made in order to optimise a cellular system include addition of new base stations, or when a base station malfunction occurs or if planning was suboptimum. Below optimal coverage leads to waste of network resources and lower quality of service (QoS).
In order to detect such holes in a cellular network, the prior art approach was to perform an expensive standardised drive test to detect possible coverage holes.
It is to be noted that in general the term “hole” is to be construed in general terms; at one extreme may be considered as a total loss of communication connectivity at a particular location. However it may be considered as a reduction in the quality of connectivity at a particular location within a network.
Active Antenna Systems (AAS) is a technology which provides improved system performance and radio network capacity as well as being a candidate to decrease radio site installation and operating costs. AAS systems had been technically challenging to implement, but recently most of the technical obstacles have been overcome. Adaptive antennas provides beam-forming capability using various parameters such as number of active antennas on horizontal or vertical plane, amplitude and phase of an antenna element, and average power so that antenna beam are able to be rotated, tilted, and formed electrically.
A sub-form of AAS is a so-called remote antenna tilt (RET), in which only antenna down-tilt is altered electrically. The methods described in the present invention can be applied to RET as well.
An aim of the embodiments is to provide a method of detecting the existence and location of holes in a communication network. A further aim is to provide a method of fixing or improving such a coverage hole. Yet a further aim is to optimise the performance of a communication network.